Alien Base: The Evidence for Extraterrestrial Colonization of Earth

Alien Base examines worldwide reports of encounters with alleged extraterrestrial beings, beginning in the early 20th century. Timothy Good considers accounts describing different kinds of visitors, arguing that reported appearances are more varied than familiar images of humanoid aliens suggest. The book brings together case material from several countries and treats these reports as part of a wider UFO record.

Good also examines claims that extraterrestrial visitors have established bases on Earth, including reports associated with the Puerto Rico area. The evidence discussed ranges from encounter narratives to allegations of hidden installations and continuing contact. Published in the late 1990s, the book presents these claims as material for investigation while advancing the possibility of an established alien presence.